Rolling of strip



Sept 1,1970 J. G. WISTREICH 3,526,114

ROLLING OF STRIP Filed July 7, 1969 4 Sheets-Sheet 1 Flal.

ATTORNEYS p 1970 I J. G. WISTREICH 3,526,114

ROLLING OF STRIP Filed July 7, 1969 4 Sheets-Sheet Z Q Q88 ENS $3 i l I 1 INVENTOR Joy/v Gsaees W/STEE/CH ATTORNEYS Se t. 1, 1970 J. G. WISTREICH ROLLING 0F STRIP 4 Sheets-Sheet 5 Filed July 7, 1969 INVENTOR gem/5 W/STRE/CH Jam 6 flaw/m ATTORNEYS p 1970 J. G. WISTREICH ROLLING OF STRIP Filed July 7, 1969 4 Sheets-Sheet L '66 X A -55 m 53 1 j 54 FIG. 5.

FIG. 6.

INVENTOR JOHN Geo/ms W/5 TRE/CH mofl/lmu ATTORNEYS United States Patent 3,526,114 ROLLING 0F STRIP John George Wistreich, Belmont, Surrey, England, assignor to The British Iron and Steel Research Association Continuation-impart of application Ser. No. 544,464, Apr. 22, 1966. This application July 7, 1969, Ser. No. 839,426 Claims priority, application Great Britain, Apr. 23, 1965, 17,339/ 65 Int. Cl. B21b 37/12 U.S. Cl. 72-9 16 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for obtaining an indication of strip shape. Three rotatable rollers are mounted in cradles designed to permit the rollers to lightly contact a moving strip in three parallel tracks evenly spaced across the width of the strip. Each roller actuates a sensing transducer which produces an electrical signal proportional to strip tension. The transducer signals are processed to produce a signal proportional to the difference in elongation between the center and edge portions of the strip.

This application is a continuation-in-part of my U.S. patent application Ser. No. 544,464, filed Apr. 22, 1966, now abandoned.

This invention relates to improvements in the rolling of strip and is particularly concerned with the control of the shape of strip.

The transverse cross-section of rolled strip is rarely, if ever, rectangular, owing to exigencies of manufacture. It is desirable, in the interests of maximum yield of end product of stated nominal thickness or surface area, to control the rolling process'so that the transverse variation of thickness of the finished strip is small, the thickness usually being greatest in the middle and falling off gradually towards the edges. Since the profile of the transverse cross-section of the finished strip is determined by the transverse profiles of the roll gaps during rolling of all the stands in which the strip has been rolled, these have to be controlled appropriately. These roll gap profiles depend partly on the camber to which the rolls have been ground and partly on factors which vary in the course rolling. Some of these factors can be adjusted and thus offer a means of control of the transverse profile of the strip. When there is a superficially apparent departure of the actual transverse profile of the strip from the desired profile, thus when the strip has local transverse undulations, the strip is said to have manifest bad shape.

It is also a fact that the elongation which rolling imparts to strip is rarely uniform across its width, giving rise to residual stresses in the longitudinal direction, which vary in magnitude across the width, are tensile in some portion or portions of the strip and compressive in the remainder. If such a strip is slitted longitudinally, at least some of the bands produced will curve in the plane of the strip and may do so to a degree that renders them unacceptable; this condition is termed latent bad shape and if pronounced is unacceptable. Furthermore, if the compressive stresses are locally comparatively large in relation to the thickness of this strip, then in these regions the strip will bow, buckle, or undulate, so that it is no more flat when laid on a plane surface; this condition is termed manifest bad shape and if pronounced is unacceptable.

The lack of uniformity of elongation across the width of the strip is caused by a transverse variation of the fractional reduction of thickness by rolling. The latter is the consequence of a mismatch between the profile of Patented Sept. 1, 1970 the transverse cross-section of the strip ahead of the rolling stand, and the transverse profile of the roll gap during rolling. Whence the need to control the latter also for the purpose of attaining good shape in the rolled strip.

In practice, the operator observes the strip as it emerges from the rolling stand and travels to the next stand or to a billy roll. If he sees local undulations in the strip, he regulates one or more of the variables affecting the transverse profile of the roll gap until the undulations disappear. In practice, this method does not cope with a mismatch which causes residual stresses without buckling, yet the stresses may be large enough to cause rejection of the strip when slit. Also, even if the strip has bad shape when laid out freely for inspection, during rolling this may be masked by the heavy tension often employed. Alternatively, the undulations may be overlooked by the operator if the strip vibrates appreciably.

The present invention consists of a method of sensing the presence of manifest and latent bad shape in strip, and apparatus therefor, which is not limited in these ways.

According to the invention in one aspect there is provided a method of obtaining an indication of strip shape, said method comprising engaging transversely spaced locations between the side edges of the strip with displaceable strip engagement means bearing against the strip, the strip engagement means being such that the said locations are separately engaged thereby, urging the strip engagement means against the strip so as to cause displacement of the strip engagement means and displace ment of the strip, the forces between the strip engagement means and the strip at said locations being equal irrespective of the extent of strip displacement at each said location, and obtaining an indication of strip displacement at each of said locations.

According to the invention in another aspect there is provided a method of obtaining an indication of strip shape, said method comprising engaging transversely spaced locations between the side edges of the strip with strip engagement means bearing against the strip, the strip engagement means being such that the said locations are separately engaged thereby, displacing the strip by the strip engagement means, the displacements of the strip at said locations being equal irrespective of the forces between the strip engagement means and the strip at each said location, and obtaining an indication of the force between the strip engagement means and the strip at each of said locations.

According to the invention in a further aspect there is provided an installation comprising a path of relative lengthwise movement between strip and apparatus for obtaining an indication of strip shape, said apparatus comprising displaceable means for engaging the strip at transversely spaced locations between the side edges thereof, the strip engagement means being such that the said locations will be separately engaged thereby, means for urging the strip engagement means against the strip so as to cause displacement of the strip engagement means and displacement of the strip out of said path, there being allowance for the strip to be displaced out of said path, said urging means being such that the forces between the strip engagement means and the strip at said locations will be equal irrespective of the extent of strip displacement at each said location, and means for obtaining an indication of strip displacement at each of said locations.

According to the invention in yet another aspect there is provided an installation comprising a path of relative lengthwise movement between strip and apparatus for obtaining an indication of strip shape, said apparatus comprising means for engaging the strip at transversely spaced locations between the side edges thereof, the strip engagement means being such that the said locations will be separately engaged thereby, means whereby there will be equal displacement of the strip out of said path as between each of said locations, there being allowance for the strip to be displaced out of said path, irrespective of the force between the strip engagement means and the strip at each said location, and means for obtaining an indication of the force between the strip engagement means and the strip at each of said locations.

The invention comprises a number of embodiments and these can be generally explained, by way of example, with reference to an intermediate stand of a tandem mill. Mid-way between adjacent rolling stands which co-operate to define a path of movement for strip there is installed an apparatus having three freely rotatable rollers, which are placed equidistant from each other, and whose axes are horizontal and contained in a plane normal to the direction of rolling. The central roller is mounted below (or above) the centre-line of the strip and the two outer rollers are below (or above) the strip at a distance somewhat less than the semi-width of the strip measured from the edges of the strip. Preferably, the two outer rollers should be situated about one sixth of the total strip width inward from the strip edge. Each roller is substantially cylindrical, but slightly crowned. The rollers are held in cradles, with the outer cradles permitting slight rocking movement of the roller axis in the plane normal to the direction of rolling. When the apparatus is not in use the rollers are arranged to be just clear of the strip surface, with an equal clearance between each roller and the strip surface (the strip here assumed to be plane and hence devoid of any buckles or undulations). In the one embodiment of this invention, the three rollers are made to bear on the strip, such that each roller applies an equal force to the strip, in a direction normal to the plane of the strip. These forces may be generated by: hydraulic, pneumatic, electrical or mechanical means; or a combination of these means. Now, if, and only if, the strip emerging from the stand ahead of the apparatus has a longitudinal stress distribution which is uniform across its width, will the strip in contact with each roll deflect an equal amount from its plane. If, however, the middle portion of the strip is elongated more than the outer portions then the strip in contact with the middle roller will be deflected more than the strip in contact with the outer rolls. Conversely if the two outer portions are elongated more than the centre, then strip in contact with the outer rollers will deflect more than the strip in contact with the central roller.

The displacement of each roller normal to the plane of the strip may be measured by means of one of the many types of transducers commonly used for this purpose and the signals fed into an electrical circuit which produces a signal proportional to the difference in elongation between the centre and edge portions of the strip and indicating whether the centre portion has been elongated more or less than the edge portions. Then this signal may be fed either into an indicator for the operators guidance, who will then adjust one or more of the rolling mill controls (for example, rolling tension; roll bending force) which aifect the transverse profile of the roll gap, until the indicator shows that the centre and edge portions of the sheet are elongated by the same amount. Alternatively the signal may be injected into a negative feedback control loop actuating one or more of the rolling mill controls (for example, rolling tension; roll bending force) which aifect the transverse profile of the roll gap, until the signal becomes zero.

In another embodiment, the three rollers are made to bear on the strip, such that each roller deflects an equal amount normal to the plane of the strip. Now, if the strip emerging from the stand ahead of the apparatus has a longitudinal stress distribution which is uniform across its width, then the force between each roller and the strip, in a direction normal to the plane of the strip, is the same. If, however, the middle portion of the strip is elongated more than the outer portions then the force between the central roller and the strip will be less than the force between the outer rollers and the strip. Conversely, if the outer portions of the strip are elongated more than the centre then the force between the strip and the outer rollers is less than the force between the central roller and the strip.

The force applied by each roller to the strip may be measured by incorporating into the mechanism supporting the rollers one of the many transducers commonly used for this purpose. The signals from the transducers are then fed into an electrical or fluid circuit which produces a signal proportional to the difference in elongation between the centre and edge portions of the strip and indicating 'whether the centre portion has been elongated more or less than the edge portions. Then this signal may be fed into an indicator for the operators guidance, who will then adjust one or more of the rolling mill controls (for example, rolling tension; roll bending force) which alfect the transverse profile of the roll gap, until the indicator shows that the centre and edge portions of the sheet are elongated by the same amount. Alternatively, the signal may be injected into a negative feedback control loop actuating one or more of the rolling mill controls (for example, rolling tension; roll bending force) which affect the transverse profile of the roll gap, until the signal becomes zero.

The invention will now be described, by way of example only, in greater detail, reference being made to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of the invention;

FIGS. 2 and 3 illustrate respectively the equal force and equal displacement embodiments of the invention;

FIG. 4 shows an electrical circuit by means of which the signals at the roller locations can be combined to give a quantitative indication of strip shape;

FIG. 5 shows how the invention can be used to control a rolling operation to produce strip of the desired shape; and

FIG. 6 is a transverse sectional view of the dotted circled portion of FIG. 5.

Turning to FIG. 1, there is illustrated apparatus consisting of three hydraulic cylinders 10 with their axes vertical, equidistant from each other, and contained in the plane which is normal to the direction of rolling; this apparatus may be installed midway between adjacent rolling stands of a multi-stand rolling mill. The central cylinder is mounted below the middle of the strip 11 and the two outer cylinders are at distances which are less than the semi-width of the strip measured from the edges of the strip, the two outer rollers preferably being situated about one sixth of the total strip width inward from the strip edge. The cylinders are provided with a common source 12 of hydraulic liquid under pressure, and are fitted with plungers 13 which are free to move vertically.

Valve means of known form and not shown in FIG. 1 will be used to enable the rollers to move upwards under the action of hydraulic pressure and to move downwards against the action of hydraulic pressure under the action of forces imparted thereto by the strip. Attached to each plunger is a cradle 14 holding a freely rotatable roller 15 which is substantially cylindrical but slightly crowned, and the axis of which is horizontal and normal to the direction of rolling. The cradles of the two outer rollers may be constructed so as to permit a small rocking movement of the roller axis about the horizontal position. The three rollers are made to bear against the underside of the strip with equal force. If, and only if, the elongation imparted to the strip by the rolling stand ahead of the roller assembly is perfectly uniform across the width of the strip, then the axes of the three rollers will align themselves on a single straight line normal to the plunger axes and parallel to the lines bisecting the two roll gaps. If, however, the middle portion of the strip is elongated more than the two outer ones then the middle roller will rise higher. Conversely, if the two outer portions are elongated more, then the outer rollers will rise above the middle one.

The vertical displacement of each roller may be measured in known manner by means of appropriate transducers 16 of known form and the signals be fed into an electrical circuit 17 of known form 'which produces a signal proportional to the difference of height of the rollers and indicating which one of the plungers is high and which is low. Then this signal may be fed into an indicator 18 of known form for the operators guidance, who will then adjust one or more of the rolling parameters (for example, rolling tension; roll bending force) which affect the transverse profile of the roll gap, until the indicator shows that the three rollers are at the same height. Alternatively, the signal may be injected into a negative feedback control loop 20 of known form actuating one or more of the rolling mill controls (for example, rolling tension; roll bending force) which affect the transverse profile of the roll gap of the rolling mill 21 until the signal becomes zero.

Although in the above example only three rollers have been specified, it will be understood that if necessary, e.g. in the rolling of very wide strip, more than three rollers might be employed. Moreover, the possibility should be envisaged that the array of roller elevations will not be disposed symmetrically about the line coinciding With the axis of the plunger of the central roller. In particular, in the three-roll arrangement, one of the outer rollers may rise higher than the other. A subsidiary circuit may be provided to transmit a signal representing such a difference for the purpose of differential regulation of the two screws in the rolling mill stand.

It will be understood that the position of the central roller assembly will be fixed in the plane containing the centre line of the strip, but the positions of the other roller assemblies can be adjusted laterally to suit the width of strip rolled.

While reference has been made to rollers vertically displaceable by vertical cylinders, this is not intended to imply a limitation to the present invention. Other arrangements are also suitable and may take the form of an arm supporting a roller at one end and pivoted at its other end, the arm being a cylinder or otherwise subjected to torque to apply a force to the strip. In such a case, transverse strip stresses can be indicated by differences in arm angles as an alternative to height differences. Also, in any of the arrangements according to the invention, the mean height or angle may be employed to indicate overall longitudinal strip tension.

As previously mentioned, in an alternative embodiment of the invention, it is the force between the strip and the three rollers which is measured. In this case, once each roller is caused to bear on the strip under the action of hydraulic pressure, such that each roller deflects an equal amount, valve means will operate to prevent downward movement of the rollers under the action of forces imparted thereto by the strip. Also, in this case, the transducers 16 would be replaced in known manner by transducers of known form for measuring force rather than displacement. By reference to the alternative embodiment previously described in which displacement rather than force is measured, it will be seen that the remaining elements of FIG. 1 may remain the same when force is measured rather than displacement.

The equal force and equal displacemen embodiments, and the manner in which the derived signals may be combined to give a quantative indication of stripshape which may be visual or which may be used to control a rolling operation, will be more fully understood from FIGS. 2 to 6. Like reference numerals as between FIGS. 1 to 6 indicate like parts.

Turning to FIG. 2 (equal force embodiment) the rollers and their cradles are not shown but will be mounted at the ends of plungers 13 as in FIG. 1. The plunger-cylinder assemblies of FIG. 2 may be mounted on a common yoke which will be raised, or lowered, to bring the rollers into proximity or initial engagement with the strip. An air/hydraulic circuit will operate to apply equal forces to the rollers irrespective of the extent of displacement of each roller and its associated strip lane. The air/hydraulic circuit comprises a shop air line 22 feeding to a stop valve 23. The air is dried, filtered, lubricated and regulated by means respectively of absorbent cylinder 24, filter 25, pressure regulators (with gauges) 26, 27 and lubricator 28. The air then passes to a standard 2-way 3-port lever operated valve 30. With the valve 30 in one position, air will pass to an air/oil reservoir 12 which provides a source of hydraulic fluid common to the plunger-cylinder assemblies. With the valve 30 in its other position, air supply from the shop line will be out OH and the air in the reservoir will exhaust to atmosphere.

On opening of stop valve 23, and with valve 30 in its full line position, the shop line air will drive hydraulic fluid (oil) out of reservoir 12 along common line 33 and into the cylinders 10 via individual lines 34 each containing a check valve 35. Hydraulic fluid leaving the cylinders 10 enters individual lines 36 each of which contains a flow regulating valve 37 and a check valve 38 and returns to reservoir 12 via common line 40. The rollers can be retracted from the strip by moving valve 30 to its dotted line position; the valve will then exhaust to atmosphere thereby depressurising reservoir 12 and allowing the rollers and their mounting to move away from the strip under their own weight (assuming of course the rollers were mounted below the strip). Alternatively, the valve 30 may be replaced by a valve and suitable piping by means of which air can be diverted to the upper side of the plungers or pistons in order to retract the rollers in which case the rollers could be mounted above the strip.

The friction of the plunger-cylinder assemblies is closely matched. The reservoir 12 has adequate volume, baffles and diffusers to prevent aeration of the hydraulic fluid. A flow regulating valve 41 enables there to be a slight bleed of air through the reservoir to help maintain it at constant pressure. Hydraulic fluid flow to and from the cylinders 10 is by different routes, with controlled flow on the downstroke of the plungers. Hence, the circuit ensures a frequent change of hydraulic fluid in the cylinders thereby reducing the risk of aeration and viscosity changes.

FIG. 3 provides an illustration of the equal displacement embodiment. This figure shows only one sensor (i.e. roller and mounting therefor together With its associated plunger-cylinder assembly, valve control and hydraulic supply). The other sensors in this embodiment would be the same as that shown in FIG. 3 and three such sensors may be arranged as shown in FIGS. 1 and 2. In FIG. 3, the plunger-cylinder assembly has associated with it a spool control valve 42 having a spool 43. The spool 43 and plunger 13 are coupled together by a rigid linkage 44. Hydraulic fluid (oil) can be fed to valve 42 from reservoir 12 via line 45; the hydraulic fluid may be expelled from reservoir 12 by means of shop line air in the manner shown in FIG. 2. Hydraulic fluid is returned from the valve 42 to the reservoir 12 via line 46. Further lines 47, 48 couple the valve 42 to opposite sides of the piston 50 of the plunger 13. The piston 50 has a through hole 51 providing a bleed to achieve dynamic stability.

The sensors of this embodiment may be rigidly mounted upon a common yoke which Will be raised, or lowered, to bring the rollers into initial engagement with the strip and to cause each roller to displace the strip an equal amount. The valve 42 and its supply 12, the linkage 44 and the lines interconnecting the valve 42, cylinder 10 and reservoir 12 comprises a simple feedback servo mechanism in which fluid pressure to the cylinders 10 is varied to maintain all the rollers at a fixed height or level irrespective of the load between a roller and the strip. The fluid pressure is varied by means of the spool valve. It will be seen that if there is a tendency for a roller to move downwards, the rigid linkage 44 would tend to move spool 43 downwards which would increase the extent to which port 52 (for line 48) is uncovered and decrease the extent to which port 53 (for line 47) is uncovered. There will thus be an increase in fluid delivery to the underside of piston 50 and a decrease in fluid delivery to the topside of piston 50. There will then be a force acting on piston 50 tending to return it and roller 15 to their original positions. The situation is of course reversed if roller 15 tends to move upwards. Under steady state conditions the rollers will be held in at-rest positions by virtue of hydraulic fluid being presented to both sides of the piston 50.

The roller displacements (in the equal force embodiment) and the loads acting on the rollers (in the equal displacement embodiment) can be measured by suitable transducers and the signals processed by the electrical circuit shown in FIG. 4 to provide a visual and quantitative indication of strip shape. Roller displacements can be measured by potentiometers of well known type, and loads acting on the rollers by strain gauge load cells of well known type. The circuit of FIG. 4 is applicable to the equal force embodiment and the left-hand, middle and right-hand displacement transducers (potentiometers) are shown within the dotted lines 54, 55 and 56 respectively. The wipers of these transducers are identified at 57, 58 and 60 respectively and will be coupled to the plungers 13 so that plunger displacement causes corresponding wiper displacement. It will be realised that to render the circuit of FIG. 4 applicable to the equal displacement embodiment, it is merely necessary to replace the displacement transducers 54, 55 and 56 by strain gauge load cells which can be incorporated into the plungers 13; such a load cell is shown so incorporated and is identified 16 in FIG. 3.

The three transducers of FIG. 4 (displacement transducers or strain gauge load cells) are supplied with supply from battery B which is stabilised by a Zener diode D The potentiometer P and shunt S are used to adjust current supply to the required level which is displayed on meter M The sensitivities of the left-hand and right-hand transducers are matched to that of the middle transducer by potentiometers P and P The output signals from the left-hand and right-hand transducers are zeroed with reference to output from the middle transducer by potentiometers P and P The difference of output voltages from the left-hand and middle transducers is amplified by A and fed to a first millivoltmeter V Similarly, the difference between the right-hand and middle transducer outputs is fed to a second millivoltmeter V after being amplifier in A Potentiometers P and P provide a means of gain adjustment for the output signal at the millivoltmeters. D8 is a decade switch which enables a stepwise calibration of the output signal to be made.

The millivoltmeters V and V have centre zeroes and thus provide visual quantitative indications of the differences between the transducer signals and also indicate whether the outer rollers are high or low compared with the centre roller.

FIGS. 5 and 6 (FIG. 5 illustrating a strip rolling mill) show with sufiicient particularity to enable the arrangement to be fully understood, the manner in which the tension distribution or shape sensor of the invention can be used to control a rolling operation to produce strip of the desired shape. The sensor is shown generally at 61 and may comprise a three roller installation according to the equal force or equal displacement embodiments as previously described. The transducer outputs from the sensor are presented to a controller 62 and combined to give a quantitative indication of strip shape or strip tension distribution. The controller 62 controls one or more rolling factors (for example, rolling tension; roll bending force) in order to achieve a desired tension distribution across the strip as measured by the sensor. Predetermined relationships can be obtained between changes in such rolling factors and changes in tension distribution as measured by the sensor 61 so that the controller 62 will use these predetermined relationships together with the sensor output to effect the necessary changes in either or both of which rolling factors to obtain the desired strip tension distribution, i.e. the desired strip shape. In practice, the controller will consist of an analogue or digital computing device and servo mechanisms using standard components and built according to well known techniques.

The rolling mill of FIG. 5 further comprises decoiler and coiler rolls 63, 64 respectively, and a four high rolling mill stand 65 having work rolls 66 and backup rolls 67. Changes in rolling tension calculated by the controller 62 would be fed along line 68 and used to control the speed of the motor driving roll 63 by way, for example, of a Ward-Leonard control system. Changes in roll bending force calculated by the controller 62 would be fed along line 70 and used in known manner to actuate hydraulic jacks 71 which are located between the opposed bearing chocks of each pair of work rolls and backup rolls. In practice, the forces in the hydraulic jacks 71 are varied so as to alter the magnitude and distribution of the forces between the work rolls and their mating backup rolls thereby altering the degree of work roll bending and thus the roll gap profile to get the desired strip shape.

What I claim is:

1. A method of obtaining an indication of strip shape, said method comprising engaging transversely spaced locations between the side edges of the strip with displaceable strip engagement means bearing against the strip, the strip engagement means being such that the said locations are separately engaged thereby, urging the strip engagement means against the strip so as to cause displacement of the strip engagement means and displacement of the strip, the forces between the strip engagement means and the strip at said locations being equal irrespective of the extent of strip displacement at each said location, and obtaining an indication of strip displacement at each of said locations.

2. A method according to claim 1 including combining said displacement indications to provide a quantitative indication of strip shape.

3. A method according to claim 2 wherein said strip shape indication is provided in the form of a visible indication. 1

4. A method according to claim 2 wherein said strip shape indication is used to control a strip rolling operation.

5. A method of obtaining an indication of strip shape, said method comprising engaging transversely spaced locations between the side edges of the strip with strip engagement means bearing against the strip, the strip engagement means being such that the said locations are separately engaged thereby, displacing the strip by the strip engagement means, the displacements of the strip at said locations being equal irrespective of the forces between the strip engagement means and the strip at each said location, and obtaining an indication of the force between the strip engagement means and the strip at each of said locations.

6. A method according to claim 5 including combining said force indications to provide a quantitative indication of strip shape.

7. A method according to claim 6 wherein said strip shape indication is provided in the form of a visible indication.

8. A method according to claim 6 wherein said strip shape indication is used to control a strip rolling operation.

9. An installation comprising a path of relative lengthwise movement between strip and apparatus for obtaining an indication of strip shape, said apparatus comprising displaceable means for engaging the strip at trans- Versely spaced locations between the side edges thereof, the strip engagement means being such that the said locations will be separately engaged thereby, means for urging the strip engagement means against the strip so as to cause displacement of the strip engagement means and displacement of the strip out of said path, there being allowance for the strip to be displaced out of said path, said urging means being such that the forces between the strip engagement means and the strip at said locations will be equal irrespective of the extent of strip displacement at each said location, and means for obtaining an indication of strip displacement at each of said locations.

10. An installation according to claim 9 including means for combining said indications of strip displacement to provide a quantitative indication of strip shape.

11. An installation according to claim 10 including a visual indicator for providing an indication of strip shape.

12. An installation according to claim 10 including a rolling mill and means for controlling the rolling operation in response to the strip shape indication.

13. An installation comprising a path of relative lengthwise movement between strip and apparatus for obtaining an indication of strip shape, said apparatus comprising means for engaging the strip at transversely spaced locations between the side edges thereof, the strip engagement means being such that the said locations will be separately engaged thereby, means whereby there will be equal displacement of the strip out of said path as between each of said locations, there being allowance for the strip to be displaced out of said path, irrespective of the force between the strip engagement means and the strip at each said location, and means for obtaining an indication of the force between the strip engagement means and the strip at each of said locations.

14. An installation according to claim 11 including meas for combining said force indications to provide a quantitative indication of strip shape.

15.. An installation according to claim 14 including a visual indicator for providing an indication of strip shape.

16. An installation according to claim 14 including a rolling mill and means for controlling the rolling operation in response to the strip shape indication.

References Cited UNITED STATES PATENTS 2,674,127 4/1954 Garrett et al. 73l59 2,809,519 10/1957 Kaestner 73l59 3,245,241 4/1966 Roberts 7216 3,248,916 5/1966 Kenyon et a1. 72--l6 3,315,506 4/1967 Schneider 729 3,318,124 5/1967 Plaisted 728 3,334,508 8/1967 Martin 729 X 3,442,104 5/ 1969 Misaka et a1 729 MHJTON S. MEHR, Primary Examiner US. Cl. XJR. 

